1. Field of the Invention
The present invention relates, in general, to a shipping container for safely transporting a nuclear fuel assembly to a nuclear power plant, etc. after the nuclear fuel assembly has been produced and, more particularly, to a lid frame for a nuclear fuel assembly shipping container, which is equipped with gap compensators adapted to minimize a gap between a nuclear fuel assembly and a lid frame for clamping the nuclear fuel assembly in a shipping container, and a shipping container for nuclear fuel assemblies.
2. Description of the Related Art
In general, nuclear fuels such as enriched uranium or mixed oxide need to be transported between various places, for instance a place where they are concentrated, a fuel rod producing place, and so on. For this transporting stage, the fuels are typically shaped like a small pellet.
These fuels require a constant level of thermal insulation and structural strength to comply with international standards, and the control of their criticality is a main concern, and a mass of enriched fuel in a shipping container should be strictly restricted such that no dangerous situations occur. Due to this requirement, the volume of fuel that can be transported in a shipping container of a certain volume is strictly restricted.
As a result, numerous shipping containers for transporting the nuclear fuel assembly have been disclosed. These shipping containers are generally designed so that a pair of lid frames are coupled to opposite long sides of the shipping container with the nuclear fuel assembly disposed therebetween so that the nuclear fuel assembly is clamped. The strength of the shipping container itself including the lid frames must be reliable, and thus the containers are typically formed of a metal material.
Meanwhile, the nuclear fuel assemblies produced at present are not limited to one type but are classified into a variety of types. As such, they are different in size from each other. In contrast, the lid frames applied to the shipping container are designed to clamp one specific type of nuclear fuel assembly. Thus, to transport all types of nuclear fuel assemblies, the lid frames should be provided so as to correspond to these types. For this reason, the manufactured lid frames are not cost-effective, and it takes much manpower and time to replace the lid frames so that they are suited to the nuclear fuel assemblies. Furthermore, a storage space for storing the manufactured lid frames is needed.
In addition, in the case of conventional nuclear fuel assembly shipping containers with clamps having the same size, since positions of spacer grids are different depending on the type of nuclear fuel assembly, the lid frames on which the clamps are disposed so as to correspond to the positions of the spacer grids should be used to transport different types of nuclear fuel assemblies. Accordingly, the lid frames should be provided depending on the type of nuclear fuel assembly.